HU200727B - Reactor for producing chlorine gas - Google Patents

Abstract

Chlorine is produced by reacting hydrogen chloride and oxygen in the presence of a chromium oxide catalyst in a reactor whose catalyst-contacting part is lined with one of lining materials represented by the following general formula (I):
    M_aX_b      (I)
wherein M means boron, aluminum, silicon, titanium, zirconium or chromium, X denotes oxygen, nitrogen or carbon, a is an integer of 1-2 and _b stands for an integer of 1-3 or with a mixture of at least two of the lining materials. The above process and reactor are effective in maintaining the activity of the catalyst.

Description

The present invention relates to a fluidization reactor for the catalytic oxidation of chlorine gas with hydrochloric acid. More particularly, the present invention relates to a reactor material used for the oxidation of hydrogen chloride with oxygen. 5

Large amounts of chlorine are produced by the electrolysis of salt water. During the electrolysis of salt water, in addition to chlorine, soda ash is also produced. Given that the demand for sodium hydroxide is lower than that of chlorine, it is difficult to prepare the brine by electrolysis, since the imbalance between the two compounds can hardly be reconciled.

On the other hand, the promotogenic chloride is largely a by-product of phosphorylation or chlorination of organic compounds. Because the generation of hydrogen chloride as a by-product is much larger than the market demand, significant quantities of hydrogen chloride need to be stored without being utilized. The cost of storage is also significant. 20

If chlorine can be effectively recovered in large quantities from discarded hydrogen chloride, then the demand for chlorine can be covered by such chlorine and chlorine produced by salt water electrolysis.

The reaction by which hydrogen chloride is oxidized to chlorine has been known for several years. It is also known, for example, from U.S. Patent No. 4,774,070, which corresponds to U.S. Patent Application Serial No. 47,231, that 30 chromium oxides are used as catalysts in such a reaction.

Recently, it has been discovered that the chromium oxide catalyst obtained especially during the calcination of chromium hydroxide retains its good activity even at relatively low temperatures, and thus the importance of oxidizing hydrogen chloride to chlorine on an industrial scale has increased, see U.S. Patent No. 4,828,815.

Although there are some unresolved issues remaining, so keep the catalytic activity. Attempts have been made to overcome this, such as those described in U.S. Patent Nos. 4,830,065 or 4,822,589, but the activity of the catalyst has not been maintained for a sufficient period of time. (Hungarian Patent Application Publication Nos. 44976 and 45946, respectively) correspond to these two documents.

We conducted several studies to address these problems. It has been found in our studies that this catalytic activity gradually decreases in the long-term reaction even when a chromium oxide catalyst is used. We have recognized that this is a consequence of the toxicity of the catalyst by iron. More specifically, it has been found that chromium oxide catalysts are prone to iron poisoning and even when the reactor contacting the catalyst contains only a small amount of iron.

Therefore, it is difficult to maintain 60 high activity over a long period of time. It has also been noticed that the reduction in catalyst activity occurs over a long period of time, even if only a very small amount of iron-containing metallic material such as nickel stainless steel is used. 65

It is an object of the present invention to provide a reactor in which the chromium oxide catalyst retains activity for a long period of time, so that the catalyst can be used in industrial applications.

The reactor of the present invention for the production of chlorine gas by the catalytic oxidation of hydrochloric acid is characterized in that the reactor wall is in contact with the catalyst with one or more compounds of formula (I).

M is leather, aluminum, silicon, titanium, zirconium or chromium;

X is oxygen, nitrogen or carbon;

a is 1 or 2; b is an integer of 1-3.

Figure 1 is a graph illustrating the oxidation of hydrogen chloride to chlorine as a function of days, using the various fluidized bed reactor materials mentioned separately in the Example and Reference Examples.

Meaning of symbols used in the figure: m = Example 1 o = Example 2 Δ = Example 3 1 = Reference example 1 s = Reference example 2

Figure 2 schematically illustrates a fluidized bed reactor according to the invention. The reactor consists of a metal tube 4, preferably a nickel tube, and an inlet gas distribution plate 2 on the bottom, preferably a ceramic plate based on sintered alumina, containing the fluidized bed catalyst 3 and the gas inlet 1 below. the reaction product outlet 6 is connected.

The height of the chromium catalyst used in the fluidized bed shall be at least 0.1 m at rest. When using a lower catalyst bed, the gases to be reacted are blown outside the fluidized bed, making it difficult to form a stable fluidized bed.

In industry, the reactor material is usually metal, glass, resin, ceramic. Several reactor materials were tested for their ability to produce chlorine in the presence of chromium oxide catalyst.

Of these materials, the resin proved to be unusable, since the reaction temperature is generally 300-500 ° C, preferably 350-450 ° C. On the other hand, metallic materials such as stainless steel, for example, in U.S. Patent Nos. 304 and 316: and nickel stainless steel, "Hastelloy B, Hastelloy C and" Inconel, were shown to be corrosion resistant. Substances containing very small amounts of iron have been a problem since iron is poisonous to the chromium oxide catalyst. This discovery led to the use of a substantially non-ferrous metallic material such as pure nickel as the reactor material.

If a reactor of this size is subjected to continuous reaction over a long period of time in industrial production, the metal component will be deposited in the pores of the catalyst, thus slowly reducing the activity of the catalyst.

Thus, further experiments were carried out to produce chlorine by the erosion of hydro-2HU 200727 Β hydrogen chloride using non-metallic materials such as glass and ceramics. These materials have been found to have no adverse effects on the catalyst and have been shown to be excellent in both heat resistance and corrosion resistance.- Although these materials alone are not strong enough to make large reactors, they are difficult to use in industry. Glass lining materials have similar problems, as they are weak against heroes, so they have to be very carefully used. Our invention is based on these findings.

In the present invention, the catalyst contact portion of the reactor is lined with a non-metallic ceramic material.

The catalyst-contacting portion of the reactor of the present invention comprises one or more compounds of formula (I):

M is leather, aluminum, silicon, titanium, zirconium or chromium; X is oxygen, nitrogen or carbon; a is an integer of 1 or 2; b is an integer of 1 to 3. Ceramic materials such as oxides such as aluminum, silicon, titanium or zirconium oxides, carbides such as silicon carbide, titanium carbide, and zirconium can be mentioned as specific examples of lining material. carbides and nitrides such as aboron nitride, soda nitride and titanium nitride. Of these, oxides are particularly preferred.

The reactor material to be coated with the liner may be iron or other economical heat-resistant metal. Although it is advantageous to use stainless steel or stainless steel or nickel stainless steel as there is a risk that the base material will corrode if the non-metallic liner material falls off. When nickel stainless steel is used, the iron content should be below 1%, especially if iron is expected to have a detrimental effect on the catalyst.

In general, when lining a parent metal with a material of formula (I), it is advantageous to apply the lining material as a film to the surface of the parent material. In addition, the material of formula (I) may be in tile bonded form or may be in a metal vessel.

The film may be formed by any suitable method, such as burning an organic precursor coating into a ceramic film, or thermally atomizing the appropriate powder with plasma or gas flame, or forming a film layer by vacuum deposition, such as physical vacuum deposition or chemical vacuum deposition.

Although there is no particular limitation on the film thickness produced by such methods, a thickness of 50200 pjn is sufficient in practice.

The term "contacting the catalyst with the reactor" includes not only the contacting with the gas introduced into the reactor, but also the contacting with the gases formed in the reactor as well as the contacting with the suspended catalyst.

The catalyst used in the reactor of the invention is primarily chromium oxide. For example, a usable catalyst can be prepared by grinding or granulating chromium oxide. The chromium chloride is obtained by precipitating and chromating the chromium (IH) salt with a base, preferably as a binder, or by preparing the catalyst in an aqueous solution of chromium salt or chromic anhydride having a pore volume of 03 to 13 µmol / g orid, and the product thus obtained is cleaved to give a bed of 20-80% by weight of chromium oxide (CnO3).

When a reactor according to the invention is used, the reaction temperature is varied depending on the activity of the chromium oxide catalyst. Generally, temperatures of from 300 to 500 ° C, preferably from 350 to 450 ° C, are employed. If the temperature is above 500 ° C, the activity of the catalyst decreases and, moreover, the corrosion effect of the gas produced is increased. On the other hand, the reaction temperature below 300 ° C results in a slight conversion and is therefore disadvantageous.

The molar ratio of hydrogen chloride to oxygen added to the reactor is 1/0 ^ 5-1 / 10 (HCVO2).

The appropriate linear velocity of the reaction gas is 10-50 cm / sec. Because of the presence of gaseous gases such as nitrogen and carbon dioxide in hydrogen chloride or oxygen, the reactor material is not damaged.

The feed gas may also contain other gas components as long as the chromium oxide catalyst is fully effective.

No difficulty arises from the structure of the reactor whether it is of solid or fluidized bed type.

If the reactor of the present invention is used, the production of chlorine on an industrial scale in the presence of a chromium oxide catalyst can be carried out by oxidation from hydrogen chloride without paying attention to the corrosion resistance of the reactor and maintaining its activity over a long period.

The present invention is illustrated by the following examples.

Example 1

Dissolve 3.0 kg of chromium oxide nonahydrate in 30 liters of deionized water. To the resulting solution was added dropwise 2.0 kg of 28% aqueous ammonia solution over 30 minutes with stirring. The resulting slurry was diluted to 200 L with water. The resulting slurry was allowed to stand overnight, then decanted several times, and the precipitate was washed. The slurry, together with colloidal silicon oxide, was added to 10% by weight of calcined material and dried in a spray dryer. The powder is cured with air at 600 ° C for three hours to give an average particle size of 50-60 µn.

The inner diameter of the nickel tube wall is 5.08 cm. The inner wall of the tube is sandblasted and then coated with "TylanoCoat (a product of Ube Industries, Ltd., a trade name for a polysilane-based heat resistant material) with a thickness of 300 µm. The tube is fired at 450 ° C to obtain an inner wall coated with a silicon oride based ceramic.

Figure 2 illustrates the reactor of the invention. The reactor was charged with 377 g of the catalyst prepared above, and then heated to 370 ° C in a fluid sand bath. At a flow rate of 3.14 Nl / min and 137 Nl / min, hydrogen chloride gas and ori

-3HU 200727 Β

6 gaseous gases are introduced while the catalyst is maintained in the iluid state. As a result of the heating, the temperature of the catalyst layer rises to 400 ° C

The gas generated in the reactor is collected by a trap. The trap is an absorption flask containing an aqueous solution of KJ solution 5 and an aqueous flask containing an aqueous solution of caustic soda. The aqueous solutions are titrated with an aqueous solution of sodium thiosulfate and hydrochloric acid to determine the amount of unreacted hydrogen chloride and chlorine formed. 10

Figure 1 shows the change in the hydrogen chloride conversion as a function of days. After forty days, we see a 68-69% conversion.

Example 2

A very small silica gel (0.177-0.063 m and 0.75 cm ³ / g pore volume) was immersed in 20 wt% aqueous solution of chromic anhydride. The immersed silica gel was dried at 120 ° C and then cured with air at 20 ° C and then 350-400 ° C for two hours.

This process is repeated three times. Finally, silica gel was calcined at 500 ° C for three hours to prepare the catalyst. The catalyst is analyzed (i.e., the catalyst contains 48% by weight of Cr2O3 and 52% by weight of silica).

As in Example 1, a silicon oxide-based ceramic material was used for lining the inner wall of the stainless steel reactor (internal diameter:

5,08 cm, U.S. Patent No. 304. Thereafter, 377 g of the catalyst prepared above were introduced into the reactor and the reaction was continued as described in Example 1 and under the same conditions.

Figure 1 shows the change in the hydrogen chloride conversion as a function of days. On the tenth day, the conversion is still 69-70%.

Example 3

Nickel-chromium stainless steel powder is thermally atomized to form a 50 μζα layer on the inner wall of a 10.16 cm nickel reactor. A 150 µm thick aluminum oxide powder is thermally sprayed over the lower liner to coat the inner wall of the reactor. 3505 g of the catalyst prepared in Example 1 were charged into the reactor.

Hydrogen chloride gas and oxygen gas are introduced into the catalyst at a flow rate of 29.2 g Nl / min and 14.6 Nl / min. The reaction was carried out as in Example 1.

Figure 1 shows the change in the hydrogen chloride conversion as a function of days. On day 11, the conversion was 70-72%. 55

4-11. example

According to Example 1, the inner wall of a 5.08 cm stainless steel reactor (U.S. Patent No. 304) is coated with the various linings shown in Table 1, 60. The reactor was charged with 377 g of the catalyst prepared in Example 1 separately. The reaction is carried out as described in Example 1 and under the same conditions. 65

Table 1 shows the initial conversion of hydrogen chloride and the extent of conversion on day 20.

Table 1

Example liner Percentage conversion number Initial Day 20 4th AI2O3 + T1O2 71-73 70-72 5th BN 71-73 69-70 6th Sic 71-73 69-70 7th TIC 71-73 69-70 8th CnCj 71-73 70-72 9th Si3N4 71-73 70-71 10th TiN 71-73 70-71 11th ZrO ₂ 71-73 70-71

Reference Example 1

A stainless steel reactor with an inside diameter of 5.08 cm (US 304) was used. The reaction was carried out according to Example 1. Figure 1 shows the change in the hydrogen chloride conversion as a function of days. On the seventh day, the conversion drops to 60%.

2. Reference Example

A nickel reactor with an inside diameter of 5.08 cm was used. The reaction was carried out according to Example 1. The

Figure 1 shows the change in the hydrogen chloride conversion as a function of days. On the fortieth day, the conversion is 62-63%.

Claims (2)

PATENT CLAIMS A fluidization reactor for the catalytic oxidation of chlorine gas with hydrochloric acid in the presence of a chromium oxide-containing catalyst consisting of a metal tube and a bottom inlet gas distributor plate containing a fluidized bed catalyst and a filter bag and a gas inlet line at the bottom. a reaction product discharge line is connected, wherein one or more of the reactor wall tangential to the catalyst M, Xb with a ceramic containing a compound of formula (I) - wherein M is boron, aluminum, silicon, titanium, zirconium or chromium; X is oxygen, nitrogen or carbon; the value of 2 or 2 b is an integer between 1 and 3. 2. A reactor according to claim 1, characterized in that it comprises alumina, silica, titanium oxide, zirconia, silicon carbide, titanium carbide, chromium carbide, boron nitride, silicon nitride or titanium. is lined with nitride.